Chapter 5: Proteins: Primary Structure

Question 1

the composition of a polypeptide chain (sequence) is limited by the ability of the
polypeptide to fold into a what

Answer 1

functional structure

Question 2

If the pI is greater than the pH what is the charge

Answer 2

positive

Question 3

If the pI is less than the pH what is the charge

Answer 3

negative

Question 4

contain subunits

Answer 4

Multisubunit proteins

Question 5

identical and/or non-identical chains

Answer 5

subunits

Question 6

A given protein is frequently obtained from a source chosen primarily for convenience

Answer 6

protein source

Question 7

produces large amounts of a foreign protein often sequesters it in what

Answer 7

inclusion bodies.

Question 8

A protein’s ionic charge, polarity, size, and ligand-binding ability influenced its

Answer 8

chromatographic behavior

Question 9

is not necessarily to minimize the loss
of the desired protein, but to eliminate selectively the other components of the mixture so that only the required substance
remains.

Answer 9

purification technique

Question 10

what pH do cells have to be to go from positive to neutral

Answer 10

high PH and PI

Question 11

what pH do cells have to be to go from negative to neutral

Answer 11

low PH and PI

Question 12

how to separate proteins by charge

Answer 12

Ion exchange chromatography
Electrophoresis
Isoelectric focusing

Question 13

how to separate proteins by size

Answer 13

size exclusion
SDS-PAGE
Gel filtration chromatography

Question 14

how to separate proteins by polarity

Answer 14

Hydrophobic interaction chromatography

Question 15

how to separate proteins by binding specificity

Answer 15

Affinity chromatography

Question 16

how to separate proteins by ligand-binding

Answer 16

affinity

Question 17

A protein in a complex mixture can be detected by its binding to its

Answer 17

corresponding antibodies

Question 18

Enzymes coupled to antibodies include alkaline phosphatase, and β-galactosidase. The amount of antigen is quantified by the
formation of a colored reaction product produced by the enzyme.

Answer 18

Direct Enzyme-Linked Immunosorbent Assay (ELISA)

Question 19

this absorbance is commonly used to measure the concentration of proteins.

Answer 19

Trp

Question 20

A protein with a what, absorbs in the
visible region of the spectrum

Answer 20

chromophore

Question 21

to change the solubility of a protein what can you do?

Answer 21

adjust the pH to approximate the isoelectric point (pI) of the desired protein

Question 22

charged molecules bind to oppositely charged
groups that are chemically linked to a matrix

Answer 22

ion exchange chromatography

Question 23

Anions bind to cationic groups on

Answer 23

anion exchanger

Question 24

most frequently used anion exchanger

Answer 24

diethylaminoethyl (DEAE) groups

Question 25

most frequently used cation exchanger

Answer 25

carboxymethyl (CM) groups

Question 26

depends on the presence of other ions that compete with the protein for binding to the ion exchanger and on the pH of the solution

Answer 26

binding affinity of a particular protein

Question 27

As the column is washed, proteins with relatively low affinities for the ion exchanger move through the column faster than proteins that bind with higher affinities

Answer 27

what to know about ion exchange

Question 28

influences the net charge of the protein

Answer 28

pH of the solution

Question 29

proteins that bind tightly to the ion exchanger can be

Answer 29

eluted

Question 30

washed through the column

Answer 30

eluted

Question 31

has a higher salt concentration or a pH that reduces the affinity with which the matrix binds the protein

Answer 31

eluant

Question 32

buffer

Answer 32

eluant

Question 33

proteins are separated by their pI values.

Answer 33

ion exchange chromatography

Question 34

molecules are separated according to their size and shape.

Answer 34

gel filtration chromatography size exclusion molecular sieve chromatography

Question 35

The stationary phase consists of gel beads containing pores that span a relatively narrow size range.

Answer 35

gel filtration chromatography size exclusion molecular sieve chromatography

Question 36

These what molecules therefore traverse the column more rapidly than what molecules that pass through the pores

Answer 36

large small

Question 37

In this technique, a molecule a ligand that specifically binds to the protein of interest is covalently attached to an inert matrix

Answer 37

affinity chromatography

Question 38

a divalent metal ion such as Zn 2+ or Ni 2+ is attached to the chromatographic matrix so that proteins bearing metal-chelating groups can be retained.

Answer 38

metal chelate affinity chromatography

Question 39

what stains the gel for SDS-PAGE

Answer 39

coomassie blue

Question 40

Separated bands may be visualized in the gel by soaking the gel in a solution of a stain (such as coomassie blue) that binds tightly to proteins.

Answer 40

SDS-PAGE

Question 41

how does electrophoresis differs from gel filtration

Answer 41

electrophoretic mobility of smaller molecules is greater than the mobility of larger molecules

Question 42

why is the pH of a SDS-PAGE usually high

Answer 42

so that nearly all proteins have net negative charges and move toward the positive electrode when the current is switched on

Question 43

what shape do proteins assume in the presence of SDS.

Answer 43

rodlike

Question 44

In SDS-PAGE, the relative mobility of proteins vary approximately linearly with what?

Answer 44

the logarithm of their molecular masses

Question 45

If a mixture of proteins is electrophoresed through a solution or gel that has a stable pH gradient in which the pH increases smoothly from anode to cathode, each protein will migrate to the position in the pH gradient corresponding to its

Answer 45

pI

Question 46

IEF can be combined with SDS-PAGE in an extremely powerful separation technique named

Answer 46

two-dimensional (2D) gel electrophoresis

Question 47

First, a sample of proteins is subjected to IEF in one direction, and then the separated proteins are subjected to SDS-PAGE in what direction

Answer 47

perpendicular direction

Question 48

is a biochemical method for separating complex mixtures of proteins into individual species.

Answer 48

2-dimensional electrophoresis (2DE)

Question 49

what is included in protein sequencing

Answer 49

2 subunits 2 different amino acids

Question 50

To be sequenced, a protein must be separated into what

Answer 50

individual polypeptides

Question 51

a procedure for removing N-terminal residues one at a time

Answer 51

Edman degradation

Question 52

the amino acid sequence can be determined by what

Answer 52

Edman degradation

Question 53

a procedure that liberates amino acids one at a time from the N-terminus of a polypeptide

Answer 53

first step of Edman degradation

Question 54

evolutionarily related proteins

Answer 54

homologous proteins

Question 55

indicate which of the protein’s residues are essential to its function, which are less significant, and which have little specific function

Answer 55

homologous proteins

Question 56

Finding the same residue at a particular position makes it an

Answer 56

invariant residue

Question 57

Changes in other amino acids with similar side chains

Answer 57

conservatively substituted

Question 58

A particular amino acid position that tolerates many different amino acid residues, indicating that the position is

Answer 58

hypervariable